CN102404257A - Narrow-band interference detecting method and device in MIMO-OFDM (Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing) system - Google Patents

Abstract

The invention discloses a narrow-band interference detecting method and device in an MIMO-OFDM (Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing) system. The method comprises the follow steps of: a pilot-frequency sub-carrier group composed of two pilot frequencies is selected in each time-frequency unit, and the two pilot frequencies in the pilot-frequency sub-carrier group are on different frequency positions of different OFDM signs; and the channel response values of two sub-carriers in the pilot-frequency sub-carrier group minus the signal power sum of the pilot-frequency sub-carrier group obtain the interference noise power value of the pilot-frequency sub-carrier group, so that the interference noise power value of each sub-carrier of the time-frequency unit is determined. The device comprises a pilot-frequency sub-carrier group selecting module and an interference noise power value determining module. The method and the device can accurately estimate the narrow-band interference information and can accurately detect the narrow-band interference position and power even if the narrow-band interference is weaker.

Description

Narrow band interference detection method and device in the MIMO-OFDM system

Technical field

The present invention relates to mobile broadband wireless and insert the field; Relate in particular to a kind of OFDM (Orthogonal Frequency Division Multiplexing; OFDM) in the system; At multiple-input, multiple-output (Multiple Input Multiple Output, MIMO) narrow band interference detection method and the device under the pattern.

Background technology

The new generation of wireless communication system needs higher transmission rate, and the OFDM technology is arisen at the historic moment.It is divided into N different parallel data stream with serial data, and parallel transmission on N carrier wave does not disturb each other, improved the transmission rate of system greatly, and the data flow of each subcarrier has lower bit rate, has improved the reliability of transmission.

OFDM will pass through data after the coded modulation as frequency domain information; Through inverse fourier transform (Inverse Discrete Fourier Transform; IDFT) transform to time domain, on channel, transmit, and at receiving terminal through inverse transformation DFT (Discrete Fourier Transform; DFT), obtain through the original modulating data behind the channel.

The channel circumstance performance of wireless communication system is varied, and this moment, traditional a single aerial system possibly be difficult to be competent at, and adopted multiaerial system then can overcome this type problem, and the MIMO technology has promptly had the ample scope for abilities.

For wireless communication system; If its transmitting antenna and reception antenna all are many; Be exactly a mimo system,, each MIMO user's performance be improved through transmitting on a plurality of transmitting antennas and on a plurality of reception antennas, receiving signal.See that from base station end up two users of MIMO needs cooperate completion, and (each user has only a transmit antennas for collaboration MIMO, spatial reuse (spatial multiplexing, SM)).

At present, mimo system mainly contains zero forcing algorithm (ZF) at the detection algorithm of receiving terminal, least-mean-square error algorithm (MMSE), maximal posterior probability algorithm (MAP).

The MAP algorithm is done well in the performance aspect MIMO decoding and the channel decoding.The MAP algorithm can obtain more accurately log-likelihood ratio (Log-likelihood ratio, LLR).

Yet the MIMO-OFDM system is under external interference; What can become is very fragile, as shown in Figure 1, and under extraneous interference characteristic condition of unknown; Narrow band interference is suppressed very difficulty; So narrow band interference is detected accurately, comprise the detection of interference position and frequency, be that to carry out the prerequisite that narrow band interference eliminates also be to guarantee that the MIMO-OFDM systematic function is necessary.

Traditional narrow band interference detection method is through certain thresholding is set narrow band interference to be detected; This mode only is applicable to the environment that narrow band interference is stronger; Detected also is the power of narrow band interference and the number of narrow band interference; Can not confirm the particular location of narrow band interference, and it is also also inapplicable for the more weak environment of narrow band interference.

Summary of the invention

The present invention provides narrow band interference detection method and the device in a kind of MIMO-OFDM system, in order to solve in the prior art when narrow band interference is more weak, can't accurately detect the problem of narrow band interference power.

Technical scheme of the present invention comprises:

Narrow band interference detection method in a kind of MIMO-OFDM system comprises step:

Steps A, the pilot subcarrier sets that selection is made up of two pilot tones in each time frequency unit, two pilot tones in the said pilot subcarrier sets are on the different frequency position of different orthogonal frequency division multiplexing symbol;

Step B, with the channel response value of two number of sub-carrier in the said pilot subcarrier sets deduct said pilot subcarrier sets signal power and; Obtain the interference noise power value of said pilot subcarrier sets, determine the interference noise power value of each subcarrier in the said time frequency unit in view of the above.

Further, the interference noise power value of each data subcarrier is the interference noise power value of a pilot tone in the said pilot subcarrier sets in the said time frequency unit, and the interference noise power value that is said pilot subcarrier sets is divided by two.

Further, also comprise behind the said step B:

Step C, determine the physical location and the record of each subcarrier on each OFDM symbol according to the subcarrier mapping relations.

Further, also comprise behind the said step C:

Step D, the different orthogonal frequency division multiplexing symbol in the said time frequency unit is carried out smoothing processing; The interference noise power value of each subcarrier of current OFDM symbol is updated to the partial information of interference noise power value of the same, physical subcarrier of a last OFDM symbol, concrete formula is:

${\mathrm{\σ}}_{n,k}^2=(1-\mathrm{\α}){\mathrm{\σ}}_{n-1,k}^2+\mathrm{\α}{\mathrm{\σ}}_{n,k}^2$

Wherein,

is the interference noise power value of the subcarrier of current OFDM symbol;

is the interference noise power value of the same, physical subcarrier of a last OFDM symbol, and α is a smoothing factor.

Further, the value of said smoothing factor α is 0.618.

Further, also comprise behind the said step D:

Step e, the interference noise power value of same sub-carrier in the many antennas is done sums on average, determine the interference noise power merging value of each subcarrier;

Step F, judge that whether the interference noise power merging value of each subcarrier surpasses the interference noise power threshold value that is provided with, if confirm that then the subcarrier on this physical location is interfered.

Further, the interference noise power threshold value of said setting is a K noise variance value doubly, and K is an integer.

Further, also comprise after the said step F:

Utilize the interference noise power merging value of each subcarrier to determine each subcarrier signals and interference plus noise ratio, it is multiplied each other as the log-likelihood ratio that weights and demodulator calculate, multiplied result is delivered to carried out narrow band interference in the decoder and eliminate.

Further, also comprise before the said steps A:

The time-domain signal that receiving terminal is received converts frequency-region signal into, obtains the channel response of each subcarrier in frequency domain in the said frequency-region signal.

Narrow band interference checkout gear in a kind of MIMO-OFDM system comprises:

Pilot sub-carrier group selection module is used for selecting the pilot subcarrier sets is made up of two pilot tones in each time frequency unit, and interior two pilot tones of said pilot subcarrier sets are on the different frequency position of different orthogonal frequency division multiplexing symbol;

Interference noise power value determination module; Be used for signal power that channel response value with said pilot subcarrier sets two number of sub-carrier deducts said pilot subcarrier sets with; Obtain the interference noise power value of said pilot subcarrier sets, determine the interference noise power value of each subcarrier in the said time frequency unit in view of the above.

Further, also comprise:

The physical location determination module is used for determining according to the subcarrier mapping relations physical location and the record of each subcarrier on each OFDM symbol;

The smoothing processing module; Be used for the different orthogonal frequency division multiplexing symbol of said time frequency unit is carried out smoothing processing, the interference noise power value of each subcarrier of current OFDM symbol be updated to the partial information of interference noise power value of the same, physical subcarrier of a last OFDM symbol;

Interference noise merges module, is used for the interference noise power value of many antenna same sub-carrier is done sums on average, determines the interference noise power merging value of each subcarrier;

Judge module is used to judge whether the interference noise power merging value of each subcarrier surpasses the interference noise power threshold value that is provided with, if confirm that then the subcarrier on this physical location is interfered.

Further, also comprise:

Interference cancellation module; Be used to utilize the interference noise power merging value of each subcarrier to determine each subcarrier signals and interference plus noise ratio; It is multiplied each other as the log-likelihood ratio that weights and demodulator calculate, multiplied result is delivered to carried out narrow band interference in the decoder and eliminate.

Beneficial effect of the present invention is following:

The pilot subcarrier sets that technical scheme according to the invention utilizes pilot signal to form is carried out the estimation of noise-plus-interference power; Can estimate narrow band interference information more exactly; Even when narrow band interference is more weak, also can the position and the power of narrow band interference be detected accurately.And then through adjusting the SINR of each subcarrier _kValue is delivered in the decoder as each tolerance weights that receive bit, can accomplish Suppression of narrow band interference.The present invention calculates simply, and the Suppression of narrow band interference effect is remarkable, can increase substantially the performance of MIMO-OFDM system.

Description of drawings

The sketch map that Fig. 1 is interfered for ofdm system;

Fig. 2 is the coding structure figure of MIMO-OFDM system;

Fig. 3 is the flow chart of the narrow band interference detection method in the MIMO-OFDM of the present invention system;

Fig. 4 is the structural representation of time frequency unit in the embodiment of the invention;

Fig. 5 estimates the analogous diagram of diverse location NI performance number for utilizing pilot tone in the embodiment of the invention;

Fig. 6 is the structured flowchart of the narrow band interference checkout gear in the MIMO-OFDM according to the invention system;

Fig. 7 is implementation result figure A of the present invention;

Fig. 8 is implementation result figure B of the present invention.

Embodiment

The present invention is directed to the defective of traditional narrow band interference detection method; A kind of more accurate narrow band interference detection method to the MIMO-OFDM system is proposed; It is combined with the MAP algorithm of mimo system receiving terminal; Even when narrow band interference is more weak, also can the position and the power of narrow band interference be detected accurately.Carry out adaptive Suppression of narrow band interference again through the method, can increase substantially the performance of MIMO-OFDM system.

See also Fig. 2, this figure is the coding structure figure of MIMO-OFDM system, among the figure, receives signal y _kCan be expressed as

y _k＝h _kx _k+NI _k

Wherein, x _kRepresent that k transmits h _kBe the channel response in frequency domain, N _kThe expression additive white noise, I _kFor disturbing, k is the subcarrier sequence number.Merge noise and interference signal, i.e. NI _k=N _k+ I _k

Soft decision decoding is adopted in the decoding of MIMO-OFDM system.In Soft decision decoding, base band demodulator calculates each and receives Euclidean distance between bit and the possible transmission bit (0 or 1) as the metric of soft-decision Viterbi decoding.

Simple on narrating considers that two MS (Mobile Station, travelling carriage) use 16QAM to modulate.16 points on the planisphere are designated as

C ₁，C ₂，...，C ₁₆

K bit of symbol is recorded as before their corresponding modulation

$C_i^k,i=\mathrm{1,2},...,16;k=\mathrm{1,2,3,4}$

Present problem is will calculate any k (k=1,2,3,4)

$\log \frac{P({s_1}^k=0|r)}{P({s_1}^k=1|r)}$

$\log \frac{P({s_2}^k=0|r)}{P({s_2}^k=1|r)}$

Because symmetry

$P({s_1}^k=b|r)={\mathrm{\Σ}}_{j=1}^{16}{\mathrm{\Σ}}_{C_i^k=b}P(s_1=C_i,s_2=C_j|r)$

$={\mathrm{\Σ}}_{j=1}^{16}{\mathrm{\Σ}}_{C_i^k=b}\frac{P(s_1=C_i,s_2=C_j,r)}{P\left(r\right)}$

$={\mathrm{\Σ}}_{j=1}^{16}{\mathrm{\Σ}}_{C_i^k=b}\frac{P\left(r\right|s_1=C_i,s_2=C_j)P(s_1=C_i,s_2=C_j)}{P\left(r\right)}$

P (s wherein ₁=C _i, s ₂=C _j) prior probability of expression modulation symbol group.Reasonably hypothesis is that this probability is to all modulation symbol combinations identical (1/256), therefore

$\log \frac{P({s_1}^k=0|r)}{P({s_1}^k=1|r)}=\log \frac{{\mathrm{\Σ}}_{j=1}^{16}{\mathrm{\Σ}}_{C_i^k=0}P\left(r\right|s_1=C_i,s_2=C_j)}{{\mathrm{\Σ}}_{j=1}^{16}{\mathrm{\Σ}}_{C_i^k=1}P\left(r\right|s_1=C_i,s_2=C_j)}$

Because have only white Gaussian noise (noisy time hypothesis disturb also be white gaussian also can) hypothesis, so have

P(r|s ₁＝C _i，s ₂＝C _j)～K(σ)×exp(-||r-H[C _i，C _j] ^T|| ²/σ ²)

Wherein K (σ) is the function of σ, owing in the calculating of LLR, can divide out, therefore need not provide concrete form.Use MAX-LOG approximate

$\ln \left\{{\mathrm{\Σ}}_n{e}^{r_n}\right\}\≈\max \left(r_n\right)$

And doing suitable abbreviation again can obtain

$\log \frac{P({s_1}^k=0|r)}{P({s_1}^k=1|r)}=\frac{1}{{{\mathrm{\σ}}_k}^2}\{\underset{j,i,C_i^k=1}{\min }{\left|\right|r-H{[C_i,C_j]}^T\left|\right|}^2-\underset{j,i,C_i^k=0}{\min }{\left|\right|r-H{[C_i,C_j]}^T\left|\right|}^2\}$

Wherein, the noise-plus-interference variance of k symbol of

expression

${\mathrm{\σ}}_k^2=\left\{\begin{array}{cc}{\mathrm{\σ}}_G^2,& H_0\\ {\mathrm{\σ}}_G^2+{\mathrm{\σ}}_I^2;& H_1\end{array}\right.$

When not having interference;

is noise variance; Can think a constant; When the calculating of metric, can ignore; When having interference; comprises interference power;

of each subcarrier is not a constant; Can cause not matching of metric if ignore; When interference is more intense; This degree of not matching can be very serious, thereby reduce performance greatly.

Optimum decoder, the position that wants accurately to calculate just necessary known noise power

interference power

of each metric that receives bit and disturb the place.The present invention is the decoding effect that reaches near optimum, at first need obtain above-mentioned several indispensable information, estimates the information of unknown disturbances.And through interfere information, the adjustment metric reaches and disturbs the effect that suppresses.

See also Fig. 3, this figure is the flow chart of the narrow band interference detection method in the MIMO-OFDM of the present invention system, and it mainly comprises the steps:

Step S101, the time-domain signal that receiving terminal is received convert frequency-region signal into.

Step S102, obtain the channel response of each subcarrier in frequency domain in the frequency-region signal that receives.

Step S103, the pilot subcarrier sets that selection is made up of two pilot tones in each time frequency unit, two pilot tones in the pilot subcarrier sets are on the different frequency position of different OFDM symbols.

Step S104, with the channel response value of two number of sub-carrier in the pilot subcarrier sets deduct pilot subcarrier sets signal power and, obtain the NI performance number of pilot subcarrier sets, determine the NI performance number of each subcarrier in the time frequency unit in view of the above;

Wherein, the NI performance number of each data subcarrier is the NI performance number of a pilot tone in the said pilot subcarrier sets in the time frequency unit, and the NI performance number that is said pilot subcarrier sets is divided by two.

Step S105, determine the physical location and the record of each subcarrier on each OFDM symbol according to the subcarrier mapping relations.

Step S106, the different OFDM symbols in the time frequency unit are carried out smoothing processing, the NI performance number of each subcarrier of current OFDM symbol is updated to the partial information of NI performance number of the same, physical subcarrier of a last OFDM symbol, concrete formula does

${\mathrm{\σ}}_{n,k}^2=(1-\mathrm{\α}){\mathrm{\σ}}_{n-1,k}^2+{\mathrm{\α\σ}}_{n,k}^2$

Wherein,

is the NI performance number of the subcarrier of current OFDM symbol;

is the NI performance number of the same, physical subcarrier of a last OFDM symbol; α is a smoothing factor, can be provided with according to the practical communication condition.

Step S107, the NI performance number of same sub-carrier in the many antennas is done sums on average, determine the NI power merging value of each subcarrier.

Step S108, judge that whether the NI power merging value of each subcarrier surpasses the NI power threshold that is provided with, if confirm that then the subcarrier on this physical location is interfered;

Wherein, the NI power threshold of setting is a K noise variance value doubly, and K is an integer.

Step S109, utilize the NI power merging value of each subcarrier to determine the SINR (Signal to Interference plus Noise Ratio) of each subcarrier, it is multiplied each other as the LLR that weights and demodulator calculate, multiplied result is delivered to carried out narrow band interference in the decoder and eliminate.

Through an embodiment the concrete implementation procedure of the method for the invention is given further detailed explanation below.

See also Fig. 4, this figure is the structural representation of time frequency unit in the embodiment of the invention, and this time frequency unit is the MIMO time frequency unit under the up PUSC pattern of 802.16e, comprises 12 number of sub-carrier altogether, and 4 pilot sub-carriers are arranged, 8 data subcarriers.Comprise pilot sub-carrier in first OFDM symbol and the 3rd OFDM symbol, all subcarriers are data subcarrier in second OFDM symbol.P1 and P3 are the pilot sub-carrier in first OFDM symbol, and P2 and P4 are the 3rd pilot sub-carrier in the OFDM symbol, and remaining subcarrier is a data subcarrier.

The detailed process of carrying out the narrow band interference detection in the embodiment of the invention is following:

For the sole user, pilot tone has only 1 pair under MIMO, and sub carrier group has only 1, can only utilize two inner pilot tones of a time frequency unit.With user 2 is example, and its pilot tone is P1 and P2, and the power calculation of k groups of subcarriers is following:

and

the total power is:

and

the signal power estimation values :

Therefore, the estimated value of the interference plus noise power in

and

is:

Since said method be to the power of 2 pilot tones on the whole time frequency unit with, if will confirm the power of each pilot tone, then make even all, i.e. P _N/ 2; 8 data subcarriers in the whole time frequency unit, we think that the NI value of each data subcarrier equates with the NI value of pilot sub-carrier, also are P _N/ 2.

Utilize pilot tone to estimate that the simulated effect of diverse location NI performance number is as shown in Figure 5.Visible by analogous diagram, the narrow band interference detection algorithm in the embodiment of the invention can be known the size and the particular location of noise and interference power effectively; Have only noise at the place of being interfered not, relatively steadily, so only need select a thresholding promptly can Interference Detection be come out.

Try to achieve the NI of continuous sub-carriers k on each OFDM symbol _kAfter the performance number, need to write down its corresponding physical position according to the subcarrier mapping relationship f, establishing the corresponding physical position is j, and j=f (k) is then arranged.So far accomplish the interfere information acquisition process.

The smoothing processing of different OFDM symbols can improve the accuracy that NI estimates to a certain extent, can be more suitable for the situation of change in practical communication system like this.Here adopt following smooth manner: the NI performance number of each subcarrier of current OFDM symbol is updated to the partial information of NI performance number of the same, physical subcarrier of a last OFDM symbol, specifically formula does

${\mathrm{\σ}}_{n,k}^2=(1-\mathrm{\α}){\mathrm{\σ}}_{n-1,k}^2+{\mathrm{\α\σ}}_{n,k}^2$

Wherein, is the NI performance number of the subcarrier of current OFDM symbol;

is the NI performance number of the same, physical subcarrier of a last OFDM symbol; α is a smoothing factor; Can be provided with according to the practical communication condition; In emulation, we get Fibonacci number is α=0.618.

Owing in actual communication systems, adopt many reception antennas mostly, improve overall performance.After utilizing above-mentioned steps to obtain the NI performance number of subcarrier; The NI performance number of same sub-carrier in the many antennas is done sums on average; The NI power merging value

of determining each subcarrier suppresses to prepare for subsequent interference, and concrete formula is following:

${\mathrm{\σ}}_k^2=\frac{\underset{i=1}{\overset{\mathrm{Rx}}{\mathrm{\Σ}}}{\mathrm{\σ}}_{i,k}^2}{\mathrm{Rx}}$

Wherein Rx is the number of antennas of receiving terminal base station side.

Because utilizing pilot tone to carry out the NI performance number estimates; And pass through smoothing processing; Its estimation is comparatively accurate; When noiseless; The NI power merging value

of each subcarrier approaches noise variance; We only need that the NI power threshold is made as the several times noise variance and get final product; When surpassing the NI power threshold as

; Then thinking has interference, otherwise

is for making an uproar at the end.Adopt the NI power threshold following to the method that interference detects:

${\mathrm{\&sigma;}}_{i,k}^2=\left\{\begin{array}{cc}{\mathrm{\&sigma;}}_N^2& {\mathrm{\&sigma;}}_{i,k}^2<\mathrm{threshold}\\ {\mathrm{\&sigma;}}_{i,k}^2& {\mathrm{\&sigma;}}_{i,k}^2\&GreaterEqual;\mathrm{threshold}\end{array}\right.$

The thresholding here is taken as K times of noise variance (K is an integer), promptly

$\mathrm{threshold}={\mathrm{k\&sigma;}}_N^2$

The such probability metrics of LLR probability that decoder need use demodulator to calculate is deciphered, and each bit LLR needs reliability measurement weights, and traditional decoder is owing to can't detect interfere information, the measurement weights SINR under disturbing _kNot accurate enough, cause decreased performance.We are through obtaining interfere information, utilize the NI power merging value of each subcarrier to determine the SINR of each subcarrier _k, it is multiplied each other as weights and LLR, multiplied result is delivered in the decoder, the LLR that finally delivers to decoder does

$L\hat{L}R={\mathrm{SINR}}_k\&times;\mathrm{LLR}$

Decoder utilizes these information, can effectively suppress to disturb.The SINR weights can be weighed the reliability of soft information, the subcarrier that is interfered, and SINR is lower, and promptly soft information reliability is relatively poor; The subcarrier that is not interfered, SINR is higher, and promptly soft information reliability is good.Through different weights, can weigh the reliability of soft information, promptly can carry out narrow band interference and eliminate through decoder, need not other calculating.Thereby can under the prerequisite that does not increase computation complexity, effectively improve systematic function.

Corresponding to said method of the present invention, the present invention also provides the narrow band interference checkout gear in a kind of MIMO-OFDM system, sees also Fig. 6, and this figure is the structured flowchart of the narrow band interference checkout gear in the MIMO-OFDM according to the invention system, and it mainly comprises:

Pilot sub-carrier group selection module is used for selecting the pilot subcarrier sets is made up of two pilot tones in each time frequency unit, and interior two pilot tones of said pilot subcarrier sets are on the different frequency position of different orthogonal frequency division multiplexing symbol.

Interference noise power value determination module; Be used for signal power that channel response value with said pilot subcarrier sets two number of sub-carrier deducts said pilot subcarrier sets with; Obtain the interference noise power value of said pilot subcarrier sets; Determine the interference noise power value of each subcarrier in the said time frequency unit in view of the above; Wherein, the NI performance number of each data subcarrier is the NI performance number of a pilot tone in the said pilot subcarrier sets in the time frequency unit, and the NI performance number that is said pilot subcarrier sets is divided by two.

The physical location determination module is used for determining according to the subcarrier mapping relations physical location and the record of each subcarrier on each OFDM symbol.

The smoothing processing module; Be used for the different orthogonal frequency division multiplexing symbol of said time frequency unit is carried out smoothing processing; The interference noise power value of each subcarrier of current OFDM symbol is updated to the partial information of interference noise power value of the same, physical subcarrier of a last OFDM symbol, concrete formula does

${\mathrm{\&sigma;}}_{n,k}^2=(1-\mathrm{\&alpha;}){\mathrm{\&sigma;}}_{n-1,k}^2+{\mathrm{\&alpha;\&sigma;}}_{n,k}^2$

Wherein,

is the NI performance number of the subcarrier of current OFDM symbol;

is the NI performance number of the same, physical subcarrier of a last OFDM symbol; α is a smoothing factor, can be provided with according to the practical communication condition.

Interference noise merges module, is used for the interference noise power value of many antenna same sub-carrier is done sums on average, determines the interference noise power merging value of each subcarrier.

Judge module is used to judge whether the interference noise power merging value of each subcarrier surpasses the interference noise power threshold value that is provided with, if; Confirm that then the subcarrier on this physical location is interfered; Wherein, the NI power threshold of setting is a K noise variance value doubly, and K is an integer.

Interference cancellation module; Be used to utilize the interference noise power merging value of each subcarrier to determine each subcarrier signals and interference plus noise ratio; It is multiplied each other as the log-likelihood ratio that weights and demodulator calculate, multiplied result is delivered to carried out narrow band interference in the decoder and eliminate.

Implementation result of the present invention such as Fig. 7 and shown in Figure 8, the QPSK modulation system is adopted in Fig. 7 emulation, the CTC1/2 coding; At 1 transmit antennas, under 4 reception antennas, through channel ITU VA60Km/h; Under interference strength INR=20dB, carry out; Adopt the present invention to carry out after narrow band interference detects and suppress, performance is approaching when noiseless, and has that performance has promoted 8dB when disturbing; The 16QAM modulation system is adopted in Fig. 8 emulation, and the CTC3/4 coding is at 1 transmit antennas; Under 4 reception antennas; Through channel ITU VA60Km/h, under interference strength INR=20dB, carry out, after employing the present invention carries out narrow band interference detection and inhibition; Performance is approaching when noiseless, and has that performance has promoted 8dB nearly when disturbing.Can be known that by Fig. 7 and Fig. 8 strong robustness of the present invention can effectively suppress narrow band interference, even do not having under the narrow band interference situation, performance can not lost yet.

Obviously, those skilled in the art can carry out various changes and modification to the present invention and not break away from the spirit and scope of the present invention.Like this, belong within the scope of claim of the present invention and equivalent technologies thereof if of the present invention these are revised with modification, then the present invention also is intended to comprise these changes and modification interior.

Claims (12)

1. the narrow band interference detection method in the MIMO-OFDM system is characterized in that, comprises step:

Steps A, the pilot subcarrier sets that selection is made up of two pilot tones in each time frequency unit, two pilot tones in the said pilot subcarrier sets are on the different frequency position of different orthogonal frequency division multiplexing symbol;

Step B, with the channel response value of two number of sub-carrier in the said pilot subcarrier sets deduct said pilot subcarrier sets signal power and; Obtain the interference noise power value of said pilot subcarrier sets, determine the interference noise power value of each subcarrier in the said time frequency unit in view of the above.

2. the method for claim 1; It is characterized in that; The interference noise power value of each data subcarrier is the interference noise power value of a pilot tone in the said pilot subcarrier sets in the said time frequency unit, and the interference noise power value that is said pilot subcarrier sets is divided by two.

3. the method for claim 1 is characterized in that, also comprises behind the said step B:

Step C, determine the physical location and the record of each subcarrier on each OFDM symbol according to the subcarrier mapping relations.

4. method as claimed in claim 3 is characterized in that, also comprises behind the said step C:

Step D, the different orthogonal frequency division multiplexing symbol in the said time frequency unit is carried out smoothing processing; The interference noise power value of each subcarrier of current OFDM symbol is updated to the partial information of interference noise power value of the same, physical subcarrier of a last OFDM symbol, concrete formula is:

${\mathrm{\&sigma;}}_{n,k}^2=(1-\mathrm{\&alpha;}){\mathrm{\&sigma;}}_{n-1,k}^2+{\mathrm{\&alpha;\&sigma;}}_{n,k}^2$

Wherein, is the interference noise power value of the subcarrier of current OFDM symbol; is the interference noise power value of the same, physical subcarrier of a last OFDM symbol, and α is a smoothing factor.

5. method as claimed in claim 4 is characterized in that, the value of said smoothing factor α is 0.618.

6. method as claimed in claim 4 is characterized in that, also comprises behind the said step D:

Step e, the interference noise power value of same sub-carrier in the many antennas is done sums on average, determine the interference noise power merging value of each subcarrier;

Step F, judge that whether the interference noise power merging value of each subcarrier surpasses the interference noise power threshold value that is provided with, if confirm that then the subcarrier on this physical location is interfered.

7. method as claimed in claim 6 is characterized in that, the interference noise power threshold value of said setting is a K noise variance value doubly, and K is an integer.

8. method as claimed in claim 6 is characterized in that, also comprises after the said step F:

Utilize the interference noise power merging value of each subcarrier to determine each subcarrier signals and interference plus noise ratio, it is multiplied each other as the log-likelihood ratio that weights and demodulator calculate, multiplied result is delivered to carried out narrow band interference in the decoder and eliminate.

9. the method for claim 1 is characterized in that, also comprises before the said steps A:

The time-domain signal that receiving terminal is received converts frequency-region signal into, obtains the channel response of each subcarrier in frequency domain in the said frequency-region signal.

10. the narrow band interference checkout gear in the MIMO-OFDM system is characterized in that, comprising:

Pilot sub-carrier group selection module is used for selecting the pilot subcarrier sets is made up of two pilot tones in each time frequency unit, and interior two pilot tones of said pilot subcarrier sets are on the different frequency position of different orthogonal frequency division multiplexing symbol;

Interference noise power value determination module; Be used for signal power that channel response value with said pilot subcarrier sets two number of sub-carrier deducts said pilot subcarrier sets with; Obtain the interference noise power value of said pilot subcarrier sets, determine the interference noise power value of each subcarrier in the said time frequency unit in view of the above.

11. device as claimed in claim 10 is characterized in that, also comprises:

The physical location determination module is used for determining according to the subcarrier mapping relations physical location and the record of each subcarrier on each OFDM symbol;

The smoothing processing module; Be used for the different orthogonal frequency division multiplexing symbol of said time frequency unit is carried out smoothing processing, the interference noise power value of each subcarrier of current OFDM symbol be updated to the partial information of interference noise power value of the same, physical subcarrier of a last OFDM symbol;

Interference noise merges module, is used for the interference noise power value of many antenna same sub-carrier is done sums on average, determines the interference noise power merging value of each subcarrier;

Judge module is used to judge whether the interference noise power merging value of each subcarrier surpasses the interference noise power threshold value that is provided with, if confirm that then the subcarrier on this physical location is interfered.

12. device as claimed in claim 11 is characterized in that, also comprises:

Interference cancellation module; Be used to utilize the interference noise power merging value of each subcarrier to determine each subcarrier signals and interference plus noise ratio; It is multiplied each other as the log-likelihood ratio that weights and demodulator calculate, multiplied result is delivered to carried out narrow band interference in the decoder and eliminate.

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